address comments

[winkyao]

Address comments

[kolbe]

@winkyao it seems like you're mis-using the configCheck (--config-check) flag. That flag is meant to cause the server to exit if config check is successful. Morgan and others agreed that another flag, --config-strict, be added, and if it is true the server should exit if the config check fails. So, --config-strict/configStrict should be checked in loadConfig().

Another issue is that importing "github.com/prometheus/common/log" as you've done here and emitting a log message to it bypasses the log facility that is used by the rest of tidb-server (which has not yet been set up at the time the config file is read). That means (I think) that this message will always be written to stderr, and never to the log file:

$ ./bin/tidb-server --config=../config.toml --config-strict=true --log-file=tidb.log
WARN[0000] config file ../config.toml contained unknown configuration options:
  status-host
  nonsense   source="config.go:393"

This doesn't seem very ideal, since it means tidb-server is emitting output to stderr when it probably shouldn't be, and it's not going to put this message in the error log, which is where an administrator will expect to look for important warnings.

The only solution I can figure is to have Config.Load return an error whether or not strict checking is enabled, and then to decide in tidb-server/main.go whether the error returned should cause the server to exit based on the value of the configStrict flag.